I actually love having the digital readout but just can't imagine why BMW didn't also provide a physical dipstick as a backup / sanity check. The risk of being singificantly low on oil is a catastrophic, $24K risk for this car and leaving a single sensor in charge of this as the only safety net is ludicrous. I am currently trying to figure out if my sensor is working properly - long story with no resolution (yet) follows...
I have owned my car for about 2.5 years - a 2013 with about 31,000 miles. It has always used a moderate amout of oil and I am used to the rate at which it uses oil (probably about 1 liter per 5K miles). A couple thousand miles after a recent oil change, my car was running at the mark halfway between full and minimum levels. I know some don't like to do this but I prefer to keep the oil in the top half of the safe range so added about a 1/4 of a liter of oil. After this, the car was running at an almost full level for some time and then gradually moved back down to the half way mark between empty and full. Then the fun began. Suddenly, it started reading completely full despite the fact that I added no oil. I know at times, the sensor is not extremely accurate but I had never seen anything like that before so I started monitoring the level very actively. After a few thousand more miles, I started to get worried since I knew that normally in that amount of time, the oil would usually have dropped at least a little but was rock solid at full. I took it in to the BMW dealership and they called and told me there were no faults on the sensor and they were sure it was fine. I expressed my significant concern and mentioned the risks of being wrong on this and told them to drain the oil and measure it since I couldn't be comfortable driving my car as I like to if I wasn't positive the oil level was sufficient. They were very snotty about this and didn't want to do it but I told them to do it, figuring an oil change a little early couldn't hurt. They confirmed that I had been almost full and the full reading made sense. I couldn't understand why my car suddenly wasn't burning oil...
I figured I would trust BMW and monitor since they just changed the oil and I figured the car was full and safe to drive for a long time. I took the car out for a long drive (about 30 mins) and the sensor never came up with a reading (?). The next two times I went out, I got a reading after the normal 6 miles or so and it was full. Then after another long drive, the reading came up as over full stating that I should have a BMW service center look at the car. I took it out once after this thinking maybe this was a fluke but again got the over full level reading.
Now my M3 is sitting in my garage waiting for my next appointement so they can hopefully explain if the sensor needs replacement or if they overfilled my car at the last oil change (when I specifically asked them to leave it between 1/4 and a 1/2 liter low so as not to overfill (a common problem when BMW changes the oil on the M3)...
I don't hate the sensor but I think it is basically unforgiveable to not provide a dipstick as a backup...
